Power amplifiers of the Class-A and Class-AB type have been employed as radio frequency (RF) power amplifiers for cellular base station and other RF systems. These amplifiers are based on the operation of a transistor primarily in its linear mode and are used in audio or other lower frequency operations. One problem with operation in linear mode is their limited ability to efficiently amplify RF signals.
In order to overcome this limitation, a new class of switching amplifiers has been developed. These amplifiers use transistors operating in a highly nonlinear mode, referred to as switch mode. The operation of transistors in the switched mode results in amplifiers with a higher efficiency than those that operate in a linear mode.
Switching mode amplifiers have seen many years of use in various electronic systems including audio and RF power amplifiers and switching power supply circuits. One example of a switching mode amplifier is a Class-D amplifier. Other examples of switching class amplifiers include, but are not limited to E, F, and S class amplifiers.
The Class-D amplifier architecture may be used in a plurality of applications. However, these amplifiers suffer from a number of problems, including device parasitics such as drain-source capacitance and lead inductance that result in high loss of power in each cycle.